The present invention relates to a non-mechanical millimeter wave beam (MMW) beam deflection device that forms and steers beams of electromagnetic radiation having wavelengths in the millimeter range, e.g., electromagnetic radiation having a free space wavelength of from 1 cm to 30 .mu.m (where 1 .mu.m=10.sup.-6 m).
There are numerous instances where it would be desirable to form a beam of electromagnetic radiation from either transmitted or received radiation and/or to scan or steer such a beam across space. Such beam steering capability would be useful, for example, in radar, telecommunications, and other similar applications. Heretofore, beam steering devices have largely been mechanical in nature, e.g., requiring the controlled physical rotation of an antenna mounted about a pivot point. Disadvantageously, mechanical beam steering devices require extensive control circuits for effectuating the desired physical movement, are limited in their ability to quickly scan or deflect a beam, and/or have elements that are prone to wear out with use. What is needed, therefore, is a beam steering device that is easily controlled, capable of a rapid scanning rate, and that has no moving parts.
One form of beam deflection is beam diffraction. In general, diffraction is the spreading or scattering of a wave motion, e.g., light, as it passes an obstacle and expands into the region that is behind the obstacle and hence not directly exposed to the incoming waves. One type of beam diffraction device known in the art is a Fresnel zone plate. Fresnel zone plates work by blocking radiation. A path of rays from a small emitting source passes through an aperture to a detection point. The rays may add either in phase or out of phase at the detection point depending upon the particular path through which the rays passes traverse in arriving at the detection point. If those rays that add out of phase or cause destructive interference are blocked from going through the aperture, then there is a large gain in the received intensity of the wave at the detection point. Such an aperture with the necessary areas blocked to prevent destructive interference is known as a Fresnel zone plate (FZP). Unfortunately, conventional FZP's require some type of physical barrier to perform the requisite blocking function. Such physical barrier necessarily limits the applicability of the FZP to a specific type of radiation, i.e., frequency and phase. What is needed is a type of FZP wherein the requisite blocking function may be performed with a dynamically induced barrier that can rapidly change its relative location and size, thereby allowing the FZP to be used for a wide variety of applications.